One object of this application to define an improvement over my previously patented stair-climbing wheelchair (U.S. Pat. No. 4,512,588) entitled xe2x80x9cStair Climbing Wheel Chairxe2x80x9d. This new design offers a narrower width and requires less driver strength and skill.
This invention relates generally to stair-climbing wheelchairs that are propelled by battery-powered electric motors and are driver-controlled.
The mobility of persons who do not enjoy the full use of their legs and feet has been restricted by the absence of an economical and dependable way of negotiating obstacles such as curbs, steps, stairs, and narrow doorways, etc. Persons who cannot walk have therefore been denied the same kind of freedom that others routinely take for granted. The absence of mobility and freedom of travel for those who cannot walk has not gone unnoticed. Many talented persons have devoted their creative genius to the fabrication of vehicles that purport to provide this desired mobility. The various solutions that have been offered from time to time may be broadly divided into three main categories as follows: 1) endless track or belt; 2) spider wheel, including 2-, 3-, 4-, 5-, and even 6-wheel configurations; and 3) other devices, including those which teach the use of articulated struts, etc.
The endless track/belt category uses tracks or belts like those employed on a bulldozer or a military tank. Examples include U.S. Pat. No. 4,154,315 to Rasmussen entitled xe2x80x9cChassis For Stair-Climbing Vehiclesxe2x80x9d; U.S. Pat. No. 4,044,850 to Winsor entitled xe2x80x9cWheelchairxe2x80x9d; and U.S. Pat. No. 4,061,199 to Last entitled xe2x80x9cChassis For A Vehicle Capable of Travelling Over Obstructions.xe2x80x9d
The spider wheel category uses wheels that have multiple spokes with a small diameter wheel at the end of each spoke. The spokes visually suggest the legs of a spider. An example of a 2-wheel spider wheel is found in U.S. Pat. No. 5,701,965 to Kamen et al. entitled xe2x80x9cHuman Transporterxe2x80x9d. Examples of 3-wheel spider wheel-type chairs include the following U.S. Pat. No. 3,241,848 to Flory entitled xe2x80x9cStair-Climbing Vehiclexe2x80x9d; U.S. Pat. No. 2,931,449 to C. A. King entitled xe2x80x9cOccupant-Controlled, Self-Propelled, Obstruction-Climbing Vehiclexe2x80x9d; and U.S. Pat. No. 2,742,973 to H. A. I. Johannesen entitled xe2x80x9cPowered Invalid Chair and Handle Control Therefor.xe2x80x9d Examples of 4-wheel spider wheel-type chairs include: U.S. Pat. No. 4,512,588 to Cox entitled xe2x80x9cStair Climbing Wheel Chairxe2x80x9d and U.S. Pat. No. 3,580,344 to Floyd entitled xe2x80x9cStair-Negotiating Wheel Chair or an Irregular-Terrain-Negotiating Vehiclexe2x80x9d. An example of a 5-wheeled device (as well as 3,4,6 or more wheels) is shown in U.S. Pat. No. 255,693 to J. C. Tauber entitled xe2x80x9cStair Truck.xe2x80x9d A 6-wheeled construction is shown in U.S. Pat. No. 3,208,544 to Colvin entitled xe2x80x9cStepping Wheel Vehicle.xe2x80x9d
Examples of constructions that employ cylinders and movable pistons include U.S. Pat. No. 3,269,478 to Joslyn entitled xe2x80x9cStair Climbing Wheel Chairxe2x80x9d; U.S. Pat. No. 3,550,709 to Hottel entitled xe2x80x9cSelf-Powered Climbing Hand Truckxe2x80x9d; and U.S. Pat. No. 3,417,831 to Lake entitled xe2x80x9cHand Truck with Power Lift.xe2x80x9d
Regrettably, most of the above-described patents have focused attention only on the problem of getting up and down stairways. It must be recognized that wheelchairs face other barriers besides stairs. In order to take full advantage of the stair-climbing capability, the wheelchair must also accommodate those other barriers.
A major problem with many wheelchairs, whether of the stair-climbing variety or otherwise, is the width of the wheelchair. Many electrically-powered wheelchairs have been proposed in the past which are too bulky. They are large and are incapable of passing through narrow doorways. In the United States many doors leading to bathrooms are only 61-centimeters (24-inches) wide. Interior trim that usually sticks out more than a few centimeters makes the practical width of these doorways about 55.9-centimeters (22-inches). An ideal wheelchair should be less than 55.9-centimeters (22-inch) to provide a minimal amount of clearance during passage into and out of a bathroom. It should still provide a wheelchair seat that is as wide as possiblexe2x80x94for the personal comfort of the driver. Most of these previous commendable efforts have provided mechanisms that are bulky and cumbersome. They cannot meet the spatial requirements of the real world. Some wheelchairs did provide access through narrow passageways and tight turning areas. However, they required upper body strength and reach for holding on to handrails for stair climbing. Some wheelchair designs failed to provide safe stability during stair climbing in the event of an unintentional loss of battery power or control system failure.
Another problem faced by some who desire improved mobility is pressure sores that develop from sitting too long in one place. Reclining the seat and seat back can relieve this problem. Such systems are available on some conventional wheelchairs and would be beneficial on stair-climbing wheelchairs as well. Steep slopes are another obstacle faced by wheelchairs.
In accordance with the present invention a stair-climbing wheelchair comprises a seat and a frame with spoked wheels on either side. There is a small wheel at the end of each spoke. A pitch-attitude sensing device and computer-controlled pitch attitude-adjusting skids on front and rear corners of the frame maintain the wheelchair seat level during stair climbing. There is at least one battery (and probably two), two motors for propelling the wheelchair, one other motor for rotating the spoked wheels, and two conventional electric-powered screw type actuators for positioning the front skids and the rear skids with caster.
Accordingly, besides the objects and advantages of the stair-climbing wheelchair described in my above patent, several objects and advantages of the present invention are:
(a) to provide a wheelchair that can accommodate stairs, steps, slopes, narrow doorways, and tight turning spaces normally seen in homes, businesses, or places visited by the public;
(b) to provide a stair-climbing wheelchair that will enter narrow doorways and still provide wide and comfortable seating;
(c) to provide a stair-climbing wheelchair that can accommodate users while requiring very minimal driver skill and strength;
(d) to provide a stair-climbing wheelchair that also functions as a normal powered wheelchair without compromise to that function;
(e) to provide a stair-climbing wheelchair with the fewest possible restrictions, such as accommodating: variable step riser and tread geometries, narrow stair width, small stair landing size, lack of hand rails, low tread friction, and tread roughness;
(f) to provide a stair-climbing wheelchair that is passively secure on the stairs even with unintended loss of power, control system failure, or loss of control system stability;
(g) to provide the driver with a smooth comfortable ride on stairs with a feeling of confidence and without fear of unsafe operations;
(h) to provide an electrically-powered wheelchair that can climb steep slopes; and
(i) to provide an electrically-powered wheelchair that can recline the seat and seat back.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.